Car quit while sitting stopped at traffic light in the left lane of a four lane road with 30+cars behind me. Good Samaritans (car load of kids) took pity on an old fart pushing his car out of the way and helped. After cool down (bout 40 minutes waiting on my truck and trailer to arrive) car cranked and I made it home.

Did the solder rework on the RCM relay board and car starts and runs fine....except that the secondary air pump now runs all of the time. That sucker is LOUD! Now driving with the 40 amp fuse pulled.

Two questions:
1) what could I have done to the RCM to create air pump issue? I only resoldered the three sets of pins at the corner of the board. Checked for any possible solder spill over but none seen with 20x magnifying glass.
2) what are consequences of running with the Secondary Air Pump off line? Seems primary function is to get the cat to light off quickly?

Fantastic write up and photos on this site. Huge shout out to tighed1!!!

Henry - 2005 XFire which is STILL waiting on its AMG engine to be installed! BTW, I need the Bracket for the Secondary Air Pump, only the SRT6 version. Seems it sits in RF corner of engine bay vs mounted to front of engine. Anyone got a SRT6 parts car??

 

You bridged a path on the RCM that has the relay for the air pump on all the time - OR a coincidence happened and the relay for that funtcion has stuck in it's closed position. Simple as that.
YOu can obtain the service manual here on the forum, go to the 'power distribution" section of the "Wiring" chapter and look for yourself The Air Pump relay circuit is simple.

 

If you stall again with engine hot and starting after cooled off might be the crankshaft position sensor.

 

Thanks for the reply.. Absolutely agree with the idea of a bridged solder joint, but I checked with a magnifying glass and saw nothing. Then to be double sure, I scratched the board between the three sets of solder that I redid.

I used three soldering guns. My Weller was too big so no go. Then I tried my hot air soldering system and it would melt the plastic at the edge of the board so I quit with that. Then I used my pencil set soldering station and it seemed to work. I will pull the RCM again to verify that there is nothing on the other side of the board.

Can the ECU have a fault that triggers the relay?

 

Great idea and that is one that I am familiar with as I had a CAS go out on this car before. My memory is foggy, but it seemed that the engine would crank but not fire when that sensor went bad - intermittently as it would run again after cooling off.

This time the engine quit and no crank - seemed a classic RCM issue. Pizza Guy suggested a solder bridge which is certainly a good idea. I am checking that once again but previous inspections with a magnifying glass did not show any solder bridges. I'll get my son with his younger eyes to look at it with me.

 

sounds like you had a crankshaft position sensor failure, then disassembled and damaged the RCM instead of replacing the crankshaft position sensor.

 

Yahoo!!! Its fixed!

There was a small bridge on the board for the Air Pump. Not the three sets of pins that I resoldered, but lower on the board. 100% sure that the hot air soldering gun I used was too hot and melted the joint between two sets of pins and created a small bridge that was seen by my son with his young eyes.

Great call from Pizza Guy who insisted that it had to be a solder bridge - and it was!

This forum rates 5 Stars and is #1 in my huge list of car specific forums in providing precise info on our Crossfires!

Henry

 

I repaired electronic equipment down to the component level from 1983 to 2011. But no more, I no longer can SEE what I'm doing at 63!

 

I wish we could get people to understand:

"My car won't start".
If the starter won't engage, it's the RCM.
If the starter is engaging, it's likely the CPS - and if' it failed/fails at high temp, it almost surely IS the CPS.

 

Myself and others still think your problem is a failing Crankshaft Position Sensor. These cars don't die hot and then restart when cool due to a problem with the RCM... That is the classic sign of a Crankshaft Position Sensor failing. "Car quit while sitting in traffic"? Of course as that sensor got hot just sitting in traffic. Buy one now and replace it before this happens again. There are YouTube videos on where it is and how to replace it. It's down in there a ways but with patience it is pop off the wire and pull 1 bolt, a 1/4" #8 torx socket if I recall, and an extension to a 1/4" ratchet will get the job done. Also, working the sensor that is in place out is easier than putting the new replacement back in as it is a tight fit. Hint... after multiple tries to get my new one seated all the way in if you look at the replacement there are 3 very tiny raised ridges on it running up it. Take a razor blade and shave those off. Then put a light film of oil on it and work it back into the hole (Pliers are helpful - standard and needle nose). Once it is back in and you have the holes aligned for the torx bolt take the bolt and lightly tape it to the Torx socket attached to the extension... reach down in there and get it started as far as you can, then attach the ratchet to tighten it and then wiggle the torx and extension off of it. If the tape stays on it you can reach down and try to yank it off or forget about it as it will fall off over time. Put small hand towel over that sharp heat shield so when you're done you arm doesn't look like you tried to pick up a stray cat... You'll know the one I'm talking about after a few sharp scrapes on your arm. I scratched mine up good before I realized what was happening.

All that being said, if ya think it was an RCM problem and you fixed it then everything above is meaningless.

 

Actually, he never made it clear: When the car died that day, did the starter engage and it refused to start? (Crank sensor)
Or....
Did the starter refuse to engage? (RCM).

MOST people who complain about the "car not starting" do not make this clear unless you ask specifically. Also, "The car cranked" means the starter engaged to MOST of us, but some say "car would not crank" when it turns over and over but does not start. So, it is VERY hard to tell what happened unless the one who posted makes it clear.

 

I’m having a sort of similar issue with my car. It has sat without starting for about 3 years. I tried jumping it yesterday and it would weakly try to turn over but the battery just just dead as a stone. Got a new battery today and now when I put the key into position 2 everything lights up but when I go to turn it on all the lights turn off and it doesn’t starter doesn’t even try at all. Also there seems to be clicking coming from the throttle body afterwards as well.

would this be one of the previously listed issues?

 

Might be the new battery needs a charge. Bring it back to the store and have them test it.

 

good point. It crossed my mind. I’ll try to jump it again with the new battery and see. Appreciate it

 

Sitting for 3 years + new battery could be as simple as corroded grounds or could be far worse. Clean the terminals that connect to the new battery and check the terminal wires for corrosion. Pull the ground to the body beside the battery and clean that up and the point of contact to the body. See if it fires up. Hopefully rodents did not take up residence and chew up wiring throughout. A few turns of the key and all lights come on for those first few turns and don't come on again could be a SKREEM issue as the car was deprived power for too long. After you've cleaned terminals and ground, try to crank. If nothing happens and dash lights no longer longer light up with subsequent cranks disconnect the battery, wait a few minutes, and reconnect. Try to crank again 2-3 times. If the lights on the dash light up those 2-3 times and after 3 times no lights on the dash light up the SKREEM could be corrupted which would equal a SKREEM/ECM/Key re-programming. Could be the RCM also that are known to fail. Scan for codes and see what comes up.

 

yea if I can’t clean them up and start it with a jump it’s going to the mechanic. I guess hoping for a quick start up after sitting that long was a little too optimistic

 

update I jumped the new battery and she started up. Ran for 5-10 mins and then died. Thinking it might need a new alternator but I guess it could also just be from residual old fuel (there was about a gallon left and I put in 4 new gallons and a amsoil hotshot)

 

I would bring the new battery back and have them fully charge it and perform a load test. You should also check for corrosion on the cables and terminals. I have had cars stall in a few minutes after jumping. Sometimes they need a complete charge.
The old fuel could possibly be causing issues, but I would resolve the battery issue first.

 

A car that sat three years? No way am I going to even try to guess at this, three year old gas and you expect the car to run right? Six month old gas can be a problem.

On that note:
There is no way I'd have allowed that old fuel to run thru those injectors. You can use a pump and pump the tank dry, then attach a fuel pressure test kit to the valve on the end of the fuel rail; you then manually close the fuel pump relay and make the pump run. While you are doing that, have a helper press and hold the release on the fuel pressure test kit and drain the fuel into a can. Once it's all pumped out, put in a gallon or two of new fuel and proceed from there.

I know it's too late for you, but for the next person.... This might seem like a lot of work and time -but it's not. And when you start the car, if it runs rough, you KNOW it's not fuel quality and since you can leave the test kit connected, if it runs rough or won't start, you know right away if you have proper fuel pressure (which is about 58psi, the car will idle down to about 20psi, but if you press the pedal it will die below about 30psi - ask me how I know!)

If you have pressure, you can move on to other items. This way, you gain knowledge of what is going on with the car quickly, which is helpful when things don[t go the way you want them to.
Oh, the OTC5630 kit is $40. Saves you SO MUCH time and frustration. When I meet some guy who "works on cars all the time" but has no fuel pressure test kit, I think: "This guy is thinking at all...." Fuel pressure HAS to be right. Our cars (and most) do not monitor fuel pressure. If your pressure is way low or way high, the ECU has NO clue. The ECU assumes the pressure is right, if it's not right, it does not compensate for too much or too little fuel - and the car either won't run or wont run right. If you struggle making that car run right, I"d order a test kit and see what you have. I've had three Roadsters, have replaced the fuel pump on two of them, one around 90,000 miles (quit working), my SE at just over 60,000 miles (started leaking).

[img]https://cimg4.ibsrv.net/gimg/www.crossfireforum.org-vbulletin/567x567/capture_954522fa78d7c6f60557a2a8701b729fccb0c842.j pg

 

Then hook up the jumper cables again from your running car's battery and hook them to the terminals of the battery in your XF. Crank and fire the XF and if it keeps running and running for an hour then that leads to an alternator issue and eliminates bad grounds, etc. I assume you don't have a multimeter that could tell right away if your XF alternator is delivering charge that is making its way to the battery while running so this is one easy test.

Be warned, when you state that you are just gonna have it towed to the shop and let them fix it. That is gonna cost a fortune as Mercedes won't touch it and Chrysler may try and run you down a rabbit hole of $ as the techs around today have no clue about how to work on Mercedes. That leaves independent euro shops who know these old SLK 320's and can work on them and they are not cheap. Maybe you have that kind of $ and maybe you don't care. If so, good for you and have at it but for those who think they want to own one of these cars and have no tools or a clue how to maintain them they become deep, deep money pits. Just my 2 cents for what it may be worth.